Two Hubble telescope images of Mars, taken about a month apart, reveal a state-sized dust storm churning near the edge of the northern polar cap. The polar storm is probably a consequence of large temperature differences between the polar ice and the dark regions to the south, which are heated by the springtime sun. The increased sunlight also causes the dry ice in the polar cap to shrink.

Mars is famous for large, planet-wide dust storms. This is the first time that such an event has been caught near the receding northern polar cap. In the top picture, the salmon-colored notch in the white northern polar cap is a 600-mile-long (1,000 kilometer-long) storm – nearly the width of Texas. In the bottom image, taken one month later, the storm has dissipated. A distinctive dust-colored, comma-shaped feature can be seen curving across the ice cap.